Processes of chemical nickel plating and baths therefor



United States Patent porta'tion Corporation, Chicago, 11]., a corporation of New York No Drawing. Application June 3, 1953, 'Serial No. 359,428

27 Claims. (01. 117-4530 Thepresent invention relates to improved processes. of chemical nickel plating of catalytic materials employingbaths of the nickel cation-hypophosphite anion type con taining stabilizing agents.

The chemical nickel plating of acatalytic material'emr ployingan aqueous bath of the nickel cation-hypophosphite anion type is based upon the catalytic reductionof nickel cations to metallic nickel and the corresponding oxidation of hypophosphite anions to phosphite anions with the evolution of hydrogen gas at the catalytic surface. The reactions take place when the body of catalyticmaterial is immersed in the plating bath, and the exterior surface of the body of catalytic material is coated with nickel. The following elements are catalytic for the oxi dation of hypophosphite and thus may be directly nickelplated: iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum. The following ele-' ments are examples of materials which may be nickelplated by virtue of the initial displacement deposition of nickel thereon either directly or through a galvanic of? feet: copper, silver, gold, beryllium, germanium, alur'n'i num, carbon, vanadium, molybdenum, tungsten, chro-' mium, selenium, titanium and uranium. The'follo-wing" elements are examplesv of non-catalytic materials which ordinarily may not be nickel-plated: bismuth,,cadmiuin, tin, lead and zinc. The activity of 'the catalytic materials varies considerably; and the following elements are particularly good catalysts in the chemical nickel plating bath: iron, cobalt, nickel and palladium. The chemical nickel plating process is autocatalytic since both the orig inal surface of the body being plated and the nickel-metal that is deposited on the surface thereof are both eata lytic; and the reduction of the nickel cations to metallic nickel in the plating bath proceeds until all of the nickel cations have been reduced to metallic nickel, in the'presence of an excess, of hypophosphi'te anions, or until all of the hypophosphite anions have been oxidized to phos'phite anions, in the presence of an excess of-nickel-cations. Actually the' reactions are slowed-down rather rapidly astime proceeds because the anions, as contrasted with the cat-ions, of the nickel salt that is dissolved in: the-plating bath combine-with the hydrogen cations toform: an acid, which, in turn, lowers the pH of the bath, and the reducingpower of the hypophosphite anions is-decreased as the pH value of the bath decreases. Moreover, there is a tendency for the early formation in the plating bath of a blaekprecipitate that comprises a random chemical reduction-of the nickel cations. Of c0urse ,.t his, formation of the black precipitate comprises a, decomposition; of the plating bath; and is particularly objectionable in that it causes the nickel deposit to be coarse, roughand frequently porous.

For the dual purposes of increasingthe stability of the plating bath (preventing the formation of the bla ckpre.- cipitate mentioned), and of increasing the normal plating rate of the bath, various baths of the present type have been suggested employing difierent additives or agents that serve either as buifers or as exaltants, For exam- 2,762,723 Patented Sept. 11, 1956 pie, in thecopending application of Gregoire Gutzeit and Abraham Krieg, Serial No. 194,656, filed November 8, 1950, now Patent No. 2,658,841, granted November 10, 1953, there is disclosed a chemical nickel plating bath of the nickel cation-hypophosphite anion type that contains as an additive a buffer in the form of a soluble salt of an organic acid, and specifically sodium acetate; and in the copending application of Gregoire Gutzeit and Ernest J Ramirez lserial No. 204,424, filed January 4, 1951, now Patent No. 2,658,842, granted November 10, 1953, there is disclosed a chemical nickel plating bath of the nickel cation-hypophosphite anion type that contains as an additive an exaltant in the form of a soluble salt of a simple short-chain saturated aliphatic dicarboxylic acid,.and specifically sodium suceinate. A typical chemical nickel plating bath of the character of that disclosed in the Gutzeit and Krieg application essentially comprisesan aqueous acid solution of a nickel salt and a hypopho sphite and a butter in the form of an alkaline acetate, the initial pH Qf the bath being within the approximate range to 5.6, the ratio between nickel ions and hypoph'oirv phiteions in the bath being between 0.25 and 0.60, the absolute concentrations ofhypophosphite ions in the bath being between 0.15 and 0.3.5 no1e/liter, and the absolute concentrations of acetate ions in the bath being ap-. proximately 0; 120 mole/liter. A' typicalchemical nickel plating bath of the character of that disclosed in the out. Z it and Ramirez. application essentially comprises aii aqueous acid solution of a nickelsalt anda hypophosphite and'an exaltant in the form of a salt of succinic acid, the initial'pHof the bath being within theapproximate range 4.3 to 6.8, the ratio between nickel ions, and hypophosphite ions in the bath being between 0.25 and 1.60, the absolute concentration of hypophos'p'hite ions in the bath. being between 0.15 and 1.20 mole/liter, and the absolute concentration of succinate ions in the bath being at least 0.05 mole/liter.

In carrying out the chemical nickel plating process'on a commercial scale employing a plating bath of the types mentioned, there may be utilized a continuous system of the character of that disclosed'in the copending application of Paul Talmey and William J. Crehan, Serial No. 222,222, filed April 21, 1951, now Patent No. 2,658,839, granted November 10, 1953; which system involves periodic or continuous regeneration of the plating bathibjy the addition thereto of appropriate ingredients for the. purpose offmaintaining substantially constant the composition of the bath.

In carrying out the chemical nickel plating process, particularly in a continuous system of the character mentioned, it has been discovered that an initially stable plating bath becomes unstable after some use, and notwithstanding the content of the buffer, or the exaltant, or both; whereby the plating bath decomposes with the formation of the'previously-mentioned black precipitates. mation of the previously-mentioned black" precipitate. (thefirst visible manifestation inthe platingbath of random reduction of the nickel cations) starts at the sur faces of suspensoids (solid particles of dust, microcrys-' talline precipitate of ferric hypophosphite, nickel phoss phite, etc.) present in the plating bath; and the presence of these suspensoids in the plating bath is evidenced. by the observation of Tyndall beams when a shaft of light. is passed through the clear filtered plating bath, even when freshly prepared.

Ihepresent invention is predicated upon the discovery that plating baths of the nickel cation-hypophosphite anion types mentioned may be stabilized to a high de' gree, without material depression of' the plating rates thereof; by the further addition thereto of a trace amount of. certain water-soluble additives of dipolar molecular character; the dipolar molecules bein'g water soluble in the true sense that a molecular solution is produced, as distinguished from a colloidal solution. In the bath, the cation of the dipolar molecule is readily dissociated and the anion of the dipolar molecule forms with the element of the suspensoid a water-insoluble product that is hydrophobic or water-repellent; the terms water-repellent and hydrophobic being taken in the broadest sense, indlcating an induced surface condition that will repel anions and dipoles of negative character. Thus the additive of dipolar molecular form is of the hydrophobic film-forming class and may take a variety of forms including the sulfhydric compounds, since these compounds have at least one functional group with aifinity for metals and a hydrophobic radical characterized by forming oriented water-repellent coatings on metal surfaces.

In accordance with one form of the invention, a trace amount of sulfide ions (if necessary) and a trace amount of a' stabilizing agent in the form of a sulfide ion controller are added to the bath; and specifically it has been discovered that plating baths of the character mentioned are stabilized by the presence therein of extremely small amounts of sulfide ions (8"), which hydrolyze, in the presence of water, to sulfhydric ions (SH'). In larger quantities sulfide ions added to the plating bath, for example as HzS, (as well as other ions, such as CN', Pb Bi Sn etc.) are a catalytic poison, and will considerably reduce the plating rate, or stop plating altogether. However, at the proper level, sulfide ions prevent random decomposition of the plating bath and the formation of the black precipitate mentioned; the minimum quantity of sulfide ions in the platingbath to achieve stability being approximately 10 parts per 1,000,000,000 parts of the plating bath by weight.

It is believed that the sulfide ions selectively attach themselves to the suspensoids in the plating bath thereby preventing the suspensoids from serving as nuclei for the random decomposition of the plating bath and the formation of the objectionable black precipitate. Specifically, the sulfide ions seem to be absorbed in an oriented manner upon the surfaces of the suspensoids giving them a hydrophobic (water repellent), which may account for the protective action in inhibiting the formation of the black precipitate. It is not necessary to have a continuous film upon the surfaces of the suspensoids, as it is sufficient -that the active centers be shielded. This mechanism is considered to be the most likely, as it is well-known that ions or dipoles are absorbed on the surfaces of solids due to localized attractive forces (free valency links), and that these same ions or dipoles repel each other due to their identical electric charges. Thus the packing of these ions or dipoles on a section of surface is a function of the radius of curvature of the surface, so that the smaller the radius of curvature the stronger the bond and the closer the packing. Accordingly, since the radii of the suspensoids are very small, the surfaces thereof will be preferentially and more densely covered than the rela tively fiat surfaces of any large body to be plated. Consequently the sulfide ions selectively attach themselves first to the suspensoids, thereby preventing their objectionable effect as nuclei for the random decomposition of the plating bath, as explained above. Moreover, the amount of the sulfide ions present should be limited so as not to have an inhibiting effect on the surface of the object being plated.

Sulfur (as such, or as inorganic, respectively organic sulfides) is generally present in very small amounts (of the order of parts per 1,000,000,000) in water and in the chemicals ordinarily used to prepare the plating bath. Elemental sulfur (particularly in a reducing medium) hydrolyzes to hydrogen sulfide; and any other soluble sulfide present in the acid plating bath will also bring about the formation of hydrogen sulfide which is volatile at elevated temperatures and thus escapes from the plating bath. As a result of this loss of sulfide ions,,by boilcopper, bismuth, tin,

-,not comprise catalytic in other words, that it ing off of the hydrogen sulfide, the plating bath becomes unstable after a short time interval, as previously noted. Wherever sulfide ions are not fortuitously present in the plating bath, they should be added, preferably as lead sulfide.

It is thought that the addition of traces of sulfide ion controllers that continuously release sulfide ions in controlled amounts in the quantities previously mentioned achieves the stabilization of the plating bath; and it is. believed that this is the mechanism of the stabilization; Of course, the cations of the sulfide ion controller must poisons in the particular range Where they are being used for stabilization; nor should they be themselves catalysts for the oxidation of hypophosphite to phosphite. For practical purposes the S" ion (respectively SH ion) can be controlled continuously by two broad classes of compounds:

(1) Inorganic sulfides that are stable and practically insoluble in the plating bath under plating conditions; i. e., in an aqueous acid solution and particularly in the range from 3.0 to 5.5, and at temperatures above 90 C., provided the cation bound to the sulfur is not a catalyst for the oxidation of hypophosphite; does not belong to group VIII of the periodic system.

(2) Organic and inorganic thio-compounds that are water-soluble and soluble under plating conditions in the plating bath, and which hydrolyze with respect to their sulfur at a rate such that a concentration of at least 10 p. p. b. (parts per billion) of liberated S" is continuously maintained in the aqueous plating bath.

Insofar as the first class is concerned, it is not necessary to supply the metallic sulfides as such, as there appears to be usually enough sulfur or sulfide ions present in the bath as impurities. It is sufiicient, therefore, merely to add traces of elements whose cations form sulfides that are stable and practically insoluble under plating con-- ditions in the aqueous acid plating bath; and an excess of these cations should be avoided as most of them are catalytic poisons. The elements that form sulfide ion controllers and thereby achieve stabilization are: lead, selenium, tellurium, tungsten, thorium, titanium, zinc, manganese and rhenium.

Insofar as the second class is concerned, the organic and inorganic thio-cornpounds are active to achieve stabilization; typical examples are soluble inorganic thiosulfates, thio-cyanate, xanthates, Aerofloats, thio-acids, thioamines (such as thiocabanilide or thiourea), organic sulfides, etc.; which organic chemicals have a very low dissociation constant (K) relative to their sulfur atoms.

Also in connection with the first class, it is noted that certain of the stabilizing agents increase the normal plating rate of the plating bath in addition to achieving stability; i. e., lead, tin and manganese; while other of these stabilizing agents improve the appearance of the plated article with reference to brightness in addition to achieving stability; i. e., selenium and tellurium.

In view of the foregoing, it is the primary object of the present invention to provide an improved nickel plating process of the character described in which the reactions involved are carried out more efficiently and under more stable conditions than heretofore, thereby rendering the process more desirable from a commercial standpoint;

Another object of the invention is to provide an improved nickel plating process of the character described,

that employs a plating bath of the nickel cation-hypophos having a pH above 2.5,-

proved nickel plating process of the character=descriled that comprises a plating bath of the nickel cation-hypophosphite anion type containing as a stabilizing agent organic sulfhydric compounds.

A further object of the invention isto provide an improved nickel plating process of the character described,

that employs a plating bath of the type mentioned containing a stabilizing agent that-increases thenormal plating rate thereof.

A further object of the invention is to provide an improved nickel plating process of the character described that employs a plating bath of the type mentioned containing a stailizing agent that etfects brightening of the nickel deposit.

the article to be nickel-plated and normally formed of a catalytic material, is properly prepared by'mechanically cleaning, degreasing and light pickling, substantially in accordance with standard practices in electroplatingprocesses. 'For example, in the nickel plating of a steel'object, it is customary mechanically to clean the rust and mill scale from the object, to degrease theobject,--and then lightly to pickle the object in a suitable-acid, such as, hydrochloric acid. The article is then immersed a suitable volume of the bath containing the proper proportions of nickel cations, hypophosphite anions, butter or exaltant, and stabilizing agent, the pH of the bath having been, if necessary, adjusted to an optimum value by the addition of an appropriate acid or base, and the bath having been heated to a temperature just below its boiling point, such as 99 C., at atmospheric pressure. Almost immediately hydrogen bubbles are formed on the catalytic surface of the steel object and escape in a steady stream from the bath, while the surface of the steel object is slowly coated with metallic nickel (containing some phosphorus). The reaction is continued until the color of the bath (green at the start) shows the absence of nickel, or until the evolution of hydrogen stops, or until it is determined that the required thickness of the nickel coating has been depositedonthe steel object. Of course, the steel object is then removed from the bath and rinsed off with water, and is then ready for use; or the bath may be continuously regenerated, the steel object being removed after the desired thickness of nickel has been deposited thereon.

With respect to the composition of the bath, it essentially comprises an aqueous solution containing nickel cations, hypophosphite anions, a butter or exaltant, and a stabilizing agent. For example, the nickel cations may be derived from nickel chloride; and the hypophosphite anions may be derived from sodium, potassium, lithium, calcium, magnesium, strontium, barium, 'etc., hypophosphites, or various combinations thereof. Specifically, a suitable bath may be formed in an exceedingly simple manner by dissolving in a hydrochloric acid-water solution nickel chloride and sodium hypophosphite; and then the buffer or exaltant and the stabilizing agent are added thereto, as explained more fully hereinafter. The desired pH of the bath is established by the eventual introduction thereinto of additional hydrochloric acid and is appropriately adjusted by the addition thereto of a weak alkali, preferably sodium bicarbonate.

The terms cation, anion, and ion as employed herein, except where specifically noted, include the total e ls quantity of the corresponding elements that are present 'inthe plating bathg i. e., bothundissociated and dissociated material. -In other words, dissociation is assumed when the terms noted are used in connection with molar ratios and concentrations in the plating bath.

The stabilizing effects of the various compounds of the first class were determined from a series ofplating tests that were made employing a standard "test plating bath of the general character of that disclosed in the previously-mentioned Gutzeit and Ramirez application, except that the chemical ingredients were highly purified; this standard testplating bath had a volume of 50 cc. and a temperature between 98 C. and 100 C.; and therein low carbon steel samples were plated that hacl-a surface area of 20 cm. and that 'had been vapor-degreased, electro-cleaned, and pickled in a 10% 'HCl solution. The standard test plating bath was produced from a solution containing nickel as nickel hypophosphite (0.09 'm. pl.), sodium hypophosphite (0.045 m. pl.), sodium succinate (0.06 m. pl.), sodium chloride (0. 18 111. pl.), and enough water to make one liter, the pH having been adjusted to a value of 4.6 with pure HCl, whereby the nickel cation/hypophosphite anion' ratio was 0.4. The stabilizing agents were then added to the standard test plating bath by measuring the proper volume from stock solutions containing 1,000 p. p. in. thereof; and the plating rates were measured in gm./cm. min. In these tests stability is indicated by the time in minutes that elapsed before black precipitate was formed; and the appearance of the nickel deposited upon thesamples was noted. In describing the appearance of a test sample, the following symbols are employed: B=

"semi-bright (satin); BB=bright; VB=very bright; S= smooth; -SR=slightly rough; R=rough; D=dull; and

Two blank plating tests were first run employing only the test samples in the standard test plating bath (without the addition of any stabilizing agent), with the following results:

Duration of Test 10 min. 60 min .Weight gain, gmS 0. 0948 051903 Plating rate, RX 10 4. 74 Sample appearance B-S .B SR Time to black ppt: None 20mins.

From the two above blank plating tests, it is apparent that the standard test plating bath is unstable since noticeable decomposition thereof takes place Within 20 minutes; and hereafter a plating bath is considered unstable in the event it decomposes within a time interval of 60 minutes.

Three stability tests were then run employing the standard test plating bath (without the test samples) at a plating temperature for the purpose of demonstrating the stabilizing elfect of lead sulfide. Specifically in the three stability tests lead sulfide in the respective amounts of 52 p. p. b., 43 p. p. b. and zero p. p. b. wereadded to the standard test plating bath, thereby establishing the respective levels of S" ions therein of 8 p. p. b., 7 p. p. b. and zero p. p. b.; whereby the respective times at which black precipitate formation was observed were: minutes, 16 minutes and 13 minutes. Accordingly, the three stability tests clearly demonstrate that the level at which the S ion is effective as a stabilizer in the'presence of lead is well-defined, the lower threshold of ef fectiveness being 'at about 8 p. p. b. and definitely in 'th range 10 to 100 p. p. b., as will appear more fully hereinafter.

In a series of these plating tests employing the 's'tan'dard test plating bath containing lead as the stabilizing agent,'derived from PbClz, the following results wereobtained:

(a) Rate tests-10 minutes p. p. m. of Pb 0. 01 0. 04 0. 07 0. 10 0. 0. 40 0.50 1. 0 10.0 50. 0 W15. gain 0. 0919 0. 0987 0. 0985 0.1037 0.0907 0. 0994 0. 0986 0.0899 0. 0938 0.0554 0. 0001 Plating Rate, RXIO 4. 59 4. 94 4. 93 5.18 4. 54 4.97 4 93 4. 49 4. 69 2. 77 Sample appearance"- B-S BB-S BB-S BB-S BB-S BB-S BB-S BB-S BB-S BB-S D Time to black ppt none none none none none none none none none none none (b) Stability tests-60 minutes p. p. m. of Pb 0 0. 01 O. 04 0. 07 0.10 i 0. 20 0. 4 1. 0 10. 0 50.0 Wt. gain 0.1892 0.2110 0. 2092 0.2122 0.1896 0. 1902 0.1948 0.1907 0.1763 0v 0001 Sample appearance BB-S BIB-S BBS BIB-S BB-S BB-S BB-S BB-S BBS D Time to black ppt 16 37 43 stable stable stable stable stable stable In a series of these plating tests employing the stand- Some of these plating tests employing the standard ard test plating bath containing tin as the stabilizing test plating bath containing lead as the stabilizing agent, agent, the following results were obtained:

(a) Rate tests10 minutes p. p. n1. of Sn 0.1 0.5 1 2 10 50 100 Wt. gain 0. 1064 0. 1072 0. 0880 0. 1135 0. 0998 0. 0910 0. 0847 Plating rate, RXlOt 5. 32 5. 36 4. 5. 68 4. 99 4. 56 4. 26 Sample appear 13-8 3-5 13-8 B-S B-S B-S B-S Time to black ppt none none none none none none none (b) Stability tests60 minutes p. p. m. of Sn n 0.1 i 0.5 1 2 10 50 100 Wt. gain 0.2189 0. 2204 0.1865 0.2220 0.1905 0. 1872 0. 1776 Sample appear B-S B-S B-S BS B-S B-S B-S Time to black ppt 40 40 25 stab stab stab stable mg results were obtamed: 40 In view of the foregoing plating test employing in the standard test plating bath tin as the stabilizing agent, the stabilizing range is about 2.0 to 50.0 p. p. m., the plating rate being increased at 2.0 p. p. m. gf oiTest'mms O 0 5 8 8% In a series of these plating tests employing the stand- '4. 68 has ard test plating bath containing manganese as the stabilizblack ppt 35 5332 g 2 35 ing agent the following results were obtained:

(a) Rate tests-10 minutes p. p.111. of Mn n 0 1 2 3.3 5 10 25 Wt. gain 0. 0948 0.9068 0.1046 0.1050 0. 0792 0. 0812 0v 0987 0.0969 Plating rate, R 10 4 4. 74 4.84 5. 23 5. 25 3.96 4. 06 4. 94 4.84 Sample appear B-S B-S BB-S BB-S BB-S BB-S B-R B-R Time to black ppt none none none none none none none none (b) Stability testsminutes p. p. m. of Mn n 0 1 2 3.3 5 10 Wt. gain 0.1903 0.1933 0. 1952 0.1943 0.1804 0.1921 Sample appear. B-SR B-SR BB-S BB-S B-SR B-SR Time to black ppt 20 30 stable stable 40 40 In view of the foregoing plating tests employing in the standard test plating bath lead as the stabilizing agent, In view of the foregoing lating tests employing in i' .:Wi1. b observedlhat about P- P- in Of P is the standard test plating bath manganese as the stabiliz- 'fiq li qi l Order 10 Obtain a Stable bath; n t about 10 ing agent, it will be observed that stabilization is obtained p. p. m. of Pbthe plating rate starts to decline. Finalat concentrations between 1.0 and 4.0 p. p. m. and that ly the peculiar phenomenon is exhibited that the trace the plating rate is somewhat enhanced.

of lead between 0.01 and 1.0 p. p. m. actually enchances In a series of these plating tests employing the standard or eiialts the plating rate, a maximum exaltation appeartest plating bath containing selenium as the stabilizing ing between 0.01 and 0.07 p. p. m. agent, the following results were obtained:

(a) Rate tests-1'0 minutes anion is reduced to the Te3 anion by" the hypophos phite.-

In a series of these plating tests employing thestandard test plating bathcontaining bismuth as the stabilizing Q0750 M778 M034 agent, the following results were obtained: I 3. 75 8.65 0.17 ample appearance 1313-8 1313-5 B s (a) Rate tesfs minutes Time to black ppt none none none i 0.5 l I 5 l0 Stabzllty tests 0 minutes 0.0654 00832 I 0.061 0.0708 3.27 I 4.10 3.05 3.54 BB-S BB-S. BB-S BB-S p. p. m. of s00 1 I 2 5 none 110118 none Wt. gain Q19 9 0,152 0,1391 I Smb'ility tests 60 minutes Sample appearance, BB'S BB-S BB-s 25 45 Stable p p. m. @1131 0.5 1- l 5 1'0 V I Wt. gain 0.1491 0.1524 0.1514 0.1442 In. view of the foregoing plating tests employing 1n Sampleappearancel. BB-S BB-S BBS BB-S the standard test plating. bath selenium as the stabilizing Tune/to black pm Stable Stable 30 agent, it will. be observed that at about 5.0 p. p. m. of selenium the bath is stabilized; and in passing, it is noted that. identical results were obtained with the. selenite and: selena-te anions with brightening of the nickel deposit.

In' view of the foregoing plating tests employing in the standard? test plating bath bismuth as the stabilizing agent, it will be: observed that stabilization occurs at'concentrations between 1.0' and 5.0 p. p. m., the maximum In a seriesof these plating tests employing thestandrate beingftlt about P'- P- ard test plating bath" containing tellurium as the stabiliz- In ser1e of these p g tests employlng the g i t: he foll wi l Were obtained; ard test plating bath contalnlng copper as the stabilizlng agent, the followlng results were obtained: I (a) Rate tests-J0 minutes (a) Rate tesrs-JO minutes p. p. m. of Te 0.1 1 5' 10 p. p. m, of Cu 1 22.1

Wt.ga1n 0. 0606 0. 0408 0. 0408' 0. 0431 gain 0. 0700 0.1059 Platlngrate;R- 10*. 3.33 2.34 2.34- 2.15 1 3.53 5. 29 Sample appearance. BS. B B-S BBS BB-S B-S B-S Time to black ppt none none none none none none (b) Stability testHaminutes p.- p. m. oLOu 5 V 10 22.1 100 221 500 Wt. gain 0.1222 0.1271 0.1204 0.1310 0.1388 0.1509 0.1850 Sample appear- BSR BB-S BB-S B-S BS D R DR Time to blackr'pp 29 42 stable stable stable stable stable Some ofthese' plating. tests employingthe standard test p 1 5 10 plating-bath containing cuprous cation (Cu) were re- 5 peated; and the following results were obtained: Wt.gain 0.0570 0. 0594 0.0504 Plating rate, .R 10 2.85 2. 07 2.- 82 Sample appearance-.. BB-S- VBS VB S Time to black ppt none none none"- p. p. m. 0! Cir 5 10 20 50 Wt. ain 0.1282 0.1210 0.1123 0.08 6 (b) Stabili y tests-60 mmutes shingle appearance-1' BS B-S B-s 3 132s: Time to black pp't 35 stable stable stable:- p.p.m.ot'1e"" 0.1 1 5 10 In view of, the foregoing plating tests employing in Wt. gain 0.1495 0.12 85 0.1218 0.1128; the standa'rcltest plating bath copper as the stabilizing gggggggggg a 15?. 3 a 2f agent, it will be observed that the cupric cation Cuis stabilizing within the range 20 to 50 p. p; m.-, while the cupro'us. cation (Cu-), is stabilizing above 10 p. p. m. Ina series of these plating testsemploying the stand- 1 5 ard test plating'bath containing rheniurn as the stabilizing.

agent, the following. results were obtained: 0.1324 0.1341 0.1388 0.1900 gagple algpeirance QED-1S gig-1S EBB-1S:

: a em ac pm 5 a e S a e S e s e (a') Rat'testS-JO minutes In view of the foregoing plating tests employing in the standard test plating bath tellurium as the stabilizing P-P' R604 1 5 25 agent, it will be observed that stabilization is obtained 7 7 at about 0.1 p. p. m. and that very bright relatively soft ggf fi 2338. 2 21, 232; .3 nickel deposits are obtained. In passing, it' is not'edthat m apparance L L the tellurate anion gives results identical to those ob- Time --PP*---- 110118 110116 none. none l (b) Stability tests-60 minutes agent, the following results were obtained:

Stability tests- 60 minutes p. p. m. of WO;

concentrations between 0.5 and 1.0 p. p. m. I When the nickel cation concentration in the plating" In view of the'foregoing plating tests employing in the standard test plating bath tungsten as the stabilizing p. p.111. orneot 1 i 25 agent, it will be observed that stabilization is obtained at a concentration rather sharply defined at 5.0 p. p.-m., the Wt. ain 0.1528 0.1526 0.1556 0.1527 5 plating rate being somewhat reduced. ggfgggggggfiz 5 In a seriesof these plating tests employing the stand ard test plating bath containing zinc as the stablhzlng Some of these plating tests employing the standard agent the fouowmg results Wsm obtamed: test plating bath containing Recation were repeated, 10 Stability tests-60 minutes and the following results were obtained:

p p.m.Zn" 1 5 10 20 30 50 ppmofRe" 1 5 10 v I v gvgg am 0. 5 03 0. gz 0.515 0. 253 0. 1 1051 0. 5095 lltgfi gggg; "11 KS 3g '%"f rimit o tii fii beiii 21 5e 41 stable same San-B Time to black ppt 28 stable stable In view of the foregoing plating tests employing in In f the foregoing Platmg tests employing 1n the standard test bath zinc as the stabilizing agent, it will the e test Plating bath Thenium as the Stabilizing be observed that stabilization is obtained at about 20.0 agent, it will be observed that the perrhenate cations and above, the plating rate being Somewhat d ReO4 is not stabllizing, whereas the R-- cation is sta- Pressmi bililing at a concentration 9 about 5 P- P- It is noted that the abovementioned metallic cations In a genes of these Platmg tests employlng the Stand all form sulfides that are both substantially insoluble ard test plating bath containing thorium as the stabilizing y in the plating bath at a PH above 5 and stable at the agent, the following results were obtained: l i temperature 90 C and b These 1 Stability .5o minutes ments all belong to the recognized qualitative analytical groups I and II, and specifically to subgroups Ia, Ib, IIb p m ofTh 5 10 and He. As a matter of fact, if both the metals that are catalysts for the oxidation of hypophosphite to phosphite wt 8 [H301 (L 1213 (11233 30 and that form unstable sulfides in boiling water or at Sample appearance B- B-S B-S pH values above 2.5 are excluded, it can be stated that Time black ppt Stable Stable, H the inorganic stabilizing elements are those of groups I',' g IIb and Ho. In Vlew of the foregou-tlg Pletmg tests: emp yms In a series of these plating tests employing the standard the Standard test befll thomlm as the stalvflrzmgagent, 1t test platingbath using a sulfur-containing molecule (in-; will be observed that the peculiar condltion is encounorganic thio compounds) as the Stabilizing agent, tered that stabilization is obtained in the range '1 to 5" f ll wi results were obtained: p. p. m., but not at higher concentrations at about 10.0 v p. p. m., the plating rate being somewhat reduced. (a) Rate tests10 minutes In a series of these plating testsemployin'g the -st-andard test plating bath containing titanium as the stabilizing p. p m of s,0;," 0.5 1 5 to agent, the following results were obtained:

Stability tests-60 minutes illtii gisa'jnani 1: 292% 2. 2% 8933 sra mple appearance. D-S D-S B-S D-R une to black ppt none none none none p.p.m.ofli"' ..l 1 5 10 Wt. gain 0.1033 0.0048 no plating Sample appearance... D D D 0.5 1 5 Time to black ppt stable stable stable 0. 1145 0. 1077 None 5.73 5.39 '0. Sample appearance. B-S B-S 1 5 I 10 Time to black ppt.- none none $5 3 iiifg. 9% 23 (b) Stability testsminutes 5 13 stab stable 7 p. p.111. OfSzOs" 0.5 1 5 v -10 In view of the foregoing plating tests employing in the standard test plating bath titanium as the stabilizing Wt. gain 0.1450 0.1458 0.1490 0.1240" agent, it will be observed that the Ticationproduces 60 iggg f gggi gi :j: 2 5 7 g ag: stabilization at about 1.0 p. p. m. with dull plating and considerable reduction in the plating rate; but that the Tication is stabilizing at about 5.0 p. p. m. with a low plating rate. In a series of these plating tests employing the standard test plating bath containing tungsten as the stabilizing 5 In view of the foregoing plating tests employing in the standard test bath sulfur (inorganic thio-compounds) as the stabilizing agent, it will be observed that the thiosulfate anion stabilizes at concentrations of-about 1.0 to

5.0 p. pfm'. while the thiocyanate anion stabilizes at bath. is increased, the amount of stabilizing agent that must be added thereto must be disproportionatelyincreased as indicated by the-plating test explained below. In carrying out these tests, a special test plating bath was produced from a solution containing nickel as'nickel hypophosphite (0.18 m. p. 1.), sodium hypophosphite (0.09 m. p. 1.), sodium succinate (0.12 m. p. 1.), sodium chloride (0.36 m. p. 1.), and enough water to make one liter, the pH having been adjusted to a value of 4.63 with pure HCl, whereby the nickel cation/hypophosphite anion ratio was :4. This special plating bath had a volume of 50cc. and: a temperatureof: between 98 C. and 100 CL; and therein low carbon steel samples were plated that had a surface area of:'20 cm. that had been vapor-degneased; electro-cleaned and: pickledi in a 10% HCl solution.

Four blank plating tests were first run employing only the test samples in the special test plating bath (without the addition of any stabilizing agent), with the following results:

Duration of test (minutes).. 10 I 10: 60 60 0.0797 0.0625 0. 1376 0. 2041 3.99 3.13 B-R B-S B-S B-R 5min. none 5 min min.

The inconsistencies in these plating. testswith. regard tov the weight gains are due to the. formation. of black precipitate. in the. plating. baths and.the trapping thereof inthe nickel deposits upon the samples.

In a series. of these. plating tests. employingthe special. test plating bath containing lead as the stabilizing agent, the following results were obtained:

(a) Rate tests-10 minutes p. p. m. of Pb" I 1 I 5 10 We. gain 0.1111 0. 0559 0.0577 0.0544' 0. 0541 Plating rate, R 10 5. 56 2. 80 2. 89 2.72 2:71 Sample appearance" BR B-S B-S- B-S B-S Time to black ppt 5 min. none none none none (b) Stability tests-60. minutes p. p. m. of Pb 1.. 1 5 10. 15 I 20 Wt. gain 0.1956 0.1924 0.1965. 0. 2090 0. 2043 Sample appearance B-R BB-S BB-S BB-S BB-S Time to black ppt; 5 min.. min. min. stable stable By comparison of the plating tests respectively involving the standard test plating bath and the special test plating bath, it will be observed that as little as 0.1 p. p; m. of Pbcation is efiective to produce stabilization in the standard test plating bath, whereas. 15.0 p.- p. 111. Pb-'- cation is required to-elfect stabilization in the special test plating bath. In other words, in order to obtain stabilization in the special test plating bath containing a 2-fold increase of nickel cation, it is necessary to provide a ISO-fold increase of Pbcation.

A few of these plating tests employing the special test plating bath containing sulfur (inorganic thio-compound) as the stabilizing agent were repeated with the (b) Stability tests-60 minutes place with 0.5 p. p. m. of CNS'ani on in the standard test plating bath more than 1.0' p. p. m. (and less than 5.0 p. p. m.) of CNS anion is requined in the special test plating bath.

The effective minimum amounts of the different ones ofthese stabilizing agents tov achieve stabilization are not only a function of nickel cation concentration in the plate ing baths, as previously explained, but. they also depend upon the particular compositions of the plating bathswith reference to other constituents. To. illustrate thisphe nomena three baths A, B andfC were preparedhaving, the particular composition. with respect to other ingredients. as follows:

Both. compositions (for. 1 liter aqueous solution):

. M. p. l.

A. Nickel as nickelhypophosphitm n 0.09

Sodium hypopliosphite 0.0.45 Sodium chloride 0.18 Sodium succinate 0.06 pH' adjusted to 4.60. with pure HCl.

B'; Nickel as nickel liypophosphite 0.09

Sodium hypophosphite 0.045 Sodium chloride 0.18 Amino-acetic ac 0118 pH. adjusted to 4;60'with pure NaOH and HCl.

C. Nickel as nickel hypophosphi'te 0.09

Sodium hypophosphite 0.045 Sodium chloride 0:18 Malic acid 0.18 Sodiumsuccinate. 0.06 pH adjusted to 4160 with pure NaOH and I-ICI'.

Plating tests" were conducted for 60 minutes at about 9 9" C. on pickled'anddegreased samples of the'cha'racter previously mentioned each having a surface area of 20- cm. and the following weight gain figures: (gm.) were obtained employingno stabilizing agent and the respec-- tive stabilizing agent's tellurium', le'ad', andthiocyanate as indicated below:

Initial N o stabi- Time to Bath pH- lizing agent blackppt.

added. in min.

A- 4. 6 0. 1892 20 4; 5 0.-1077 29 B as; 02176 22 B 8.5 0. 1597 4 followmg results Time tov Telluriume-p. p. m.

Bath Initial black (a) Rate tests-10 mmutes pH. ppt., W

min. 1 5" 1.0v m. of CNS 1 5 p p None None.

Wt. gain 0.1364 0.0025 None Plating rate, RXlO. 6.82 0.13 20-30.

Sample appearance BBS B-S None.

Time to black ppt none none None .thcse baths are formed of sufficiently pure Time to Lead-p. p. m.

Bath Initial black p pv min. 0.07 l 5 10 4. 6 None 4. 5 None 6.5 None 8.5 20-30 50 4. 5 None 21 5. 50 None 0. 2443 0.2380 0.2320

Time to Thicyanatep. p. m. Bath Initial black p m min 1 v 5 4. 6 None 0.1685 no plating 4. 5 None 0.1552 0.0016 I 0.0008 6. 5 None 0. 2006 no plating 8.5 20-30 0. 2908 no plating 4. 5 None 0.2131 0. 0014 0. 0010 5.50 None 0.2284 0.0028 0. 0006 From the above table, it will beobserved that in bath B, at pH 8.5, while Tecation actually increases the plating rate, Pbcation is of no effect within the range set forth. However, in other tests (not reported in detail at this point) it has been demonstrated that Pbcation is effective at 75 p. p. m. (decreased plating rate; 0.1467 gms. gained) and atlOO p. p. m. (increased plating rate: 0.1852 gms. gained).

-].n passing, it is noted that the stabilizing agents can be introduced into the plating bath by other means than by adding a solutionof a soluble salt; i. .e., the plating can be performed in the plating bath in the presence of a strip of metallic lead, providing there are enough S" ions in thebath as previously explained. s

'In the foregoing plating tests, steel samples were used for studying the actions of the stabilizing agents, but the same stabilizing eflfects have been found to hold true in the'plating'of other materials such as brass, copper, alum'inum, manganese, etc.

-As previously pointed out, initially stable plating baths of the character disclosed in the Gutzeit and 'Krieg application -and in the Gutzeit and Ramirez application are sometimes fortuitously obtained by the production of these baths from commercial grades of chemical ingredients by virtue of a content of extraneous sulfur and heavy metals cations (lead, copper, manganese, titanium, etc.) as impurities; however, this result is not obtained when chemical ingredients. Moreoverthe baths even though initially stable due to the fortuitous circumstance mentioned become un-- stable in use, in continuous plating systems, and particularly in the system disclosed in the Talmey and Crehan application. This rendering unstable of the initially stable plating baths after use is brought about fundamentally by the loss therefrom, by boiling 01f, of hydrogen sulfide. Thus in order both-to sure continued stability of the plating bath in use, the inclusion therein of the'stabilizing elements as previously described is highly desirable.

Specifically in carrying out ticularly when a continuous plating operation of the character of that disclosed in the Talmey and Crehan application is employed, it is recommended that the selected stabilizing agent be fed periodically or continuously into the plating bath along with the other regenerating chemicals (particularly the nickelcation and the hypophosphite anion) so as to keep the levelthereof substantially constant and at'that required, as previously explained; for example, the simplest and jectionable with respect to overa relatively wide range of concentration, stance aslead or tin, tion thereof within the efiective range by the required adobtain'initial stability and to in-- the present method, par-:1

safest procedure is to select a stabilizing agent that is known -to be active, and unobdecreasing the plating rate,

such for in- 4 and to keep the level of concentraard-test plating 1,000 p. p. m. of the organic 16 dition' thereof to the plating bath along with the other regeneratingingredients as noted above.

Turning now to the stabilizing agents of the second class or organic thio-compound type, the sulfhdric flotation collectors have been found to be particularly effective. Specifically the xanthates, of the general formula:

Where R is an alkyl group, or a hydroaromatic, respectively an aryl group linked through aliphatic substituents, and M an alkali metal (Na or K), are excellent sulfide controllers. The most common commercial xanthates (and commercial names) that have been found effective are:

Potassium ethyl xanthate (Z-3) Sodium ethyl xanthate (Z4) Sodium isopropyl xanthate (Z-9) Potassium n-butyl xanthate (Z7) Potassium sec-butyl xanthate (Z8) Potassium amyl xanthate (ZS) Pentasol xanthate (Z6) Potassium hexyl xanthate (ZlO) The thiophosphates also belong to the sulfhydric class and are well-known as flotation collectors; they comprise reaction products of phosphorus pentasulfide with various organic compounds such as phenols, alcohols, mercaptans or thioalcohols, amines and nitriles; the products with phenols and alcohols are in common use, known as Aerofloats and have the general structural formula:

no SH (or M) wherein R is an alkyl or aryl radical and M an alkali. metal or ammonium ion.

Other useful members of the sulfhydric class are mer captans or thioalcohols; thiocarbanilide (diphenyl thiourea); diphenyl thicarbazide; mercaptobenzothiazole' (Flotagen); dithiocarbamates; trithiocarbamates, etc. Also the oxidation products of the above compound (organic sulfides) are eflective.

The stabilizing efiect of the various compounds of the second class were determined from a series of plating tests that were made employing the standard test plating bath and plating conditions previously described; and plating. rates'were again measured in gms/cmF/min. In these plating tests the stabilizing agents were added to the standbaths from stock solutions containing molecule.

In a series of these plating tests employing the standard test plating bath containing potassium ethyl xanthate as the stabilizing agent, the following results were obtained:

(a) Rate tests-10 minutes p. p. m. of xanthate u 1 i 5 10 50 250 i gain, gms 0. 0953 0.0980 0.0085 0. 0910 0. 0031 Plating rate, RXlO 4.76 4.90 4. 92 4. 0.01 Sample appearance. B-S B-S B-S D-S D-R- Time to black ppt. none none none none none (b) Stability testsminutes Time to black ppt n stable stable In view of the foregoing plating tests employing in the standard test plating bath potassium ethyl xanthate as the stabilizing agent, it will be observed that stabilization is achieved at 5.0 p. p. m. with a slight increase in the plating rate up to about 10.0 p. p. m. and perhaps to 50.0 p. p. m.

In a series of these plating tests employing the standard 5 lizing agent, the following results were obtained:

(a) Rate tests-1'0 minutes test plating bath containing potassium methyl Xanthate as the stabilizing agent, the following results were obtained: thiomalic acid 1 5 50 10 (a) Rate tests-10 mmutes Wt. gain, gms 0.0768 0.0900 0.0903 0. 0928 0. 0040 glatinlg rate R 10 8g %5g 4 5 1 ifig 5). (g amp e appearance... P- P- Of Xamhate O 5 10 25 Time to black ppt 5 10 none none none ggg ggg 3. 22 (b) Stability tests-60 minutes pH begin 4.. 58 pH end 3. 95 Sample appearance B-S B-S B-S B-S p. p. m. thlomalie acid 0.5 1 5 10 50 Time to black ppt none none none none gvt. gitin, gms 0. 1 415 0. gag 0. 5 443 0 mg) amp e appearan (b) Stablhty tests 60 mmmes Time to black ppt stable stable stable stable Ofxanthater 0 1 5 10 50 p In view of the foregoing plating tests employing in the 0 1448 0 1477 0 1517 0 1522 0 1540 standard test plating bath thiomalic acid :as the stabilizing 58 58 58 58 4 58 25 agent, it will be observed that stabilization is obtained besa 1 R 2.6}? at 2.0 4 2.6]? 2%) tween 1.0 and 10.0 p. p. m. i 5 132 ppt: 10 10 15 50 55 Stable In a series of these plating tests employing the standard test plating bath containing thiocarbanilide :as the stabi- In view of the foregoing plating tests employing in the standard test plating bath potassium methyl Xanthate as the stabilizing agent, it will be observed that stabilization is achieved at 50.0 p. p. m. and above.

Comparing the two foregoing groups of plating tests respectively employing in the standard test plating bath potassium ethyl xanthate and potassium methyl xanthate as stabilizing agents, it will be observed that about ten times as much potassium methyl Xanthate as potassium ethyl xanthate is required to achieve the same degree of stabilization in the standard test platirig'bath, thereby in-' dicating that the longer carboxylic chain is clearly funcional in the formation of a hydrophobic aliphatic chain product upon the suspensoids.

In a series of these plating tests employing a standard test plating bath containing sodium Aerofloat as the stabilizing agent, the following results were obtained:

Stability tests-60 minutes lizing agent the following results were obtained:

stable stable In these plating tests since thiocarbanili'de is not watersoluble, it was first dissolved in ethylene glycol and then introduced into the standard test plating baths, whereby it was observed that thiocarbanilide stabilizes at 5.0 p. p. m. and above, plating being inhibited at 50.0 p. p. m.

In a series of these plating tests employing a standard test plating bath containing thiourea as a stabilizing agent,

the following results were obtained:

p. p. in. sodium Aerofloat 1 5 1O 20 30 300 Wt. gain, gms 0.1353 0.1384 0.1415 0.1415 0.1523 0.0060 0.0018 Sample app0arance B-R B-S B-S B-S B-S D no plating Time to black ppt 16 48 stable stabl stable stable stable Stable In view of the foregoing plating tests employing in the 5 Stability testsminutes standard test plating bath sodium Aeroflo'at as the sta- 4 bilizing agent, it will be observed that stabilization is obp. plm. thiourea 1 .5 10 50 tained from 5-20 p. p. m. with an increased plating rate V V at the latter concentration. gvt i n ms 405 1 g gaig amp eappear no pating In 3 im of these i i testes enlPloymg the fif 60 Time to black ppt stable stable stable stable test plating bath containing sodium Aerofloat B as the stabilizing agent, the following results were obtained:

Stability tests60 minutes p.p.m.Sodiu1nAero- 'e float B 5 10 20 a0 50 300 Wt. gain, glIlS 0.1386 0.1459 0.1454 0.150 0.0020 0.0016 Sample appearance B-S BB-S BB-S BB-S D no plating Time to black ppt 33 stable stable stable stable stable 'stable' In view of the foregoing plating tests employing in the standard test plating bath :sodium Aerofloat B as the stabilizing agent, it will be observed that stabilization is In view of the foregoing plating test employing in the standard test plating baththiourea as the stabilizing agent, it will be observed that stabilization is achieved within the 76 range'ifrom about 1.0 to 10.0 p. p. m.

Again it is pointed out that when the nickel cation concentration in the plating bath is increased, the amount of stabilizing "agent that must be added thereto must be disproportionately increased indicated by the plating tests appearing below utilizing the special test plating bath and plating procedure previously described.

In a series of these plating tests employing the special test plating bath containing sodium Aerofloat as the stabilizing agent, the following results were obtained:

(a) Rate tests-J minutes p. p. m. sodium 1 5 "Aerofloat Wt. gain, gms 0.1309 0. 1360 0. 1361 0. 1311 0. 1212 Plating rate RX10 6. 55 6. 80 6. 81 6. 56 6. 06 Sample appearance BB-R BB-S BB-S 1313-8 1313-8 Time to black ppt. 5 none none none none (b) Stability tests-60 minutes p. p. m. Sodium 1 5 1o 15 20 Aerofloat Wt. gain, gms 0. 2020 0. 2429 0v 2511 0.2313 0. 2302 Sample appoarance BB-R BB-R BB-S 1313-8 1313-5 Time to black ppt-.. 5 20 40 58 stable By comparison of the plating tests respectively involving the standard test plating bath and the special test plating bath, it will be observed that as little as 5.0 p. p. m. of sodium Aerofioat is eifective to produce stabilization in the standard test plating bath, whereas 20.0 p. p. m. of sodium Aerofloat is required to effect stabilization in the special test plating bath. However, in the plating tests employing the special test plating bath, the plating rate is substantially increased and the sample appearance is brighter.

While the effective minimum amounts of the difierent ones of these organic stabilizing agents to achieve stabilization are a function of nickel cation concentration in the plating baths, as explained above, they are otherwise independent of the particular compositions of the plating baths with reference to other constituents. This is'probably due to the fact that they do not form complexes with such constituents as malic acid, lactic acid, amino-acetic acid, etc. Thus the stabilizing agents of the organic type possess this advantage with respect to the stabilizing agents of the inorganic type, previously described. Moreover, when the stabilizing agents of the organic type are used in proper amounts, they do not decrease the plating rate over wide ranges, and they tend to increase substantially sample brightness; and H1OI'60V6I'5'ih6Y do not appear to have any adverse action on the adhesion of the nickel plating upon the base metal.

Furthermore, due to the exceedingly small amount of sulfide ion controller required in a plating bath, it is immaterial from an economic standpoint which one among those described above is selected and in what quantity it is used within the individual operating range thereof, providing that the plating rate is not decreased.

It will be understood that the stabilizing agents described are particularly well-suited for use in continuous nickel plating processes involving regeneration of the ingredients of the character disclosed in the Talmey and Crehan application.

It should be noted that analytic methods for the exac per, silver, gold, palladium and determintion of trace quantities of ingredients of the order of magnitude herein employed (for example, sulfide ion controller in parts per 1,000,000,000 parts of the plating bath) are not now available in the art; however, these trace quantities as set forth were determined by carefully eliminating all possible sources of sulfide and other trace ions from the plating bath, and then by adding known quantities thereof to the bath. Accordingly, it

will be appreciated that the trace quantities given are approximate, but are readily understandable by those nickel 20 skilled in the art, as levels above the maximum obtainable purity of ingredients employed in the formation of the plating bath.

In view of the foregoing, it is apparent that there has been provided an improved process of chemical nickel plating of catalytic materials employing baths of the nickel cation-hypophosphite anion type containing stabilizing agents, as well as improved baths therefor. Further, it will be understood that great advantages are obtained by the utilization of the present process, particularly in continuous nickel plating operations, since such processes frequently involve exceedingly large volumes of the nickel plating bath that must be stabilized.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with an aqueous bath consisting essentially of nickel ions and hypophosphite ions and also containing sulfide ions and a sulfide ion controller, both said sulfide ions and said sulfide ion controller being present in solution in said bath only in controlled trace amounts that together are not greater than about 200 parts per 1,000,000 parts of said bath by Weight so as not substantially to reduce the plating rate of said bath, said sulfide ion controller forming with said sulfide ions a thio-compound that is both stable and substantially insoluble in said bath so as to maintain the dissociated sulfide ion concentration in said bath of the order of magnitude of 1 part per 100,000,000 parts of said bath by weight in order to inhibit random decomposition of said ba 2'. The process of chemically plating With nickel a bodyessentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with a hot aqueous bath consisting essentially of nickel ions and hypophosphite ions and also containing sulfide ions and a sulfide ion controller, the temperature of said bath being above C. and the pH of said bath being in the range 3.0 to 8.5, both said sulfide ions and said sulfide ion controller being present in solution in said bath only in controlled trace amounts that together are not greater than about 200 parts per 1,000,000 parts of said bath by weight so as not substantially to reduce the plating rate of said bath, said sulfide ion controller forming with said sulfide ions a thio-compound that is both stable and substantially insoluble in said bath so as to maintain the dissociated sulfide ion concentration in said bath of the order of magnitude of 1 part per 100,000,000 parts of said bath by weight in order to inhibit random decomposition of said bath.

3. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copplatinum, which comprises contacting said body throughout a given time interval with an aqueous bath consisting essentially of ions and hypophosphite ions and also containing sulfide ions and a sulfide ion controller, both said sulfide ions and said sulfide ion controller being present, in solution in said bath only in controlled trace amounts that together are not greater than about 200 parts per 1,000,000 p'artsof said bath by weight so as not substantially to reduce the plating rate of said bath, said sulfide ion controller forming with said sulfide ions a thio-compound that is both St ble 11d substantially insoluble in said bath so as to maintain the dissociated sulfide ion concentration in said bath of the order of magnitude of 1 part per 100,000,000 parts of said bath by weight in order to inhibit random decomposition of said bath, maintaining the temperature of said bath above 90 C. throughout said given time interval, maintaining the pH of said bath in the range 3.0 to 8.5 throughout said given time interval, and adding to said bath during said given time interval trace quantities of both said sulfide ions and said sulfide ion controller so as to maintain said controlled trace amounts thereof in said bath throughout said given time interval.

4. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with an aqueous bath consisting essentially of nickel ions and hypophosphite ions and an additive consisting of a thio-compound having a dipolar molecular structure including a dissociable cation and a hydrophobic anion forming with said element a compound insoluble in said bath, said additive being present in solution in said bath only in a controlled trace amount not greater than about 200 parts per 1,000,000 parts of said bath by Weight so as not substantially to reduce the plating rate of said bath and so as to inhibit random decomposition of said bath.

5. The process of chemically plating with nickel a solid body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with an aqueous bath consisting essentially of nickel iron and hypophosphite ions and an additive consisting of a thio-compound that forms an oriented hydrophobic film on said body, said additive being present in solution in said 'bat-h only in .a controlled trace amount not greater than about 200 parts per 1,000,000 parts of said bath by weight so as not substantially to reduce the plating rate of said bath .and so as to inhibit random decomposition of said bath.

6. The process set forth in claim 5, wherein said additive consists essentially of a sulfhydric compound.

7. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with an aqueous bath consisting essentially of nickel ions and hypophosphite ions, said bath also containing a thio-compound that is both non-catalytic for the oxidation of hypophosphite and stable in said bath, said thio-compound being present in solution in said bath only in a controlled trace amount not greater than about 200 parts per 1,000,000 parts of said bath by weight so as not substantially to reduce the plating rate of said bath and so as to maintain the dissociated sulfide ion concentration in said bath only in a controlled trace amount of the order of magnitude of 1 parts per 100,000,000 parts of said bath by weight in order to inhibit random decomposition of said bath.

8. The process set forth in claim 7, wherein said thiccompound consists essentially of an organic thio-compound.

9. The process set forth in claim 7, wherein said thiocompound consists essentially of an Xanthate.

10. The process set forth in claim 7, wherein said thio-compound consists essentially of a thio-plrosphate.

11. The process set forth in claim 10, wherein said thio-phosphate has the general structural formula:

where R is a radical selected from the group consisting of alkyl and aryl, and X is an ion selected from the 22 group consisting of hydrogen, alkali metal and ammonium.

12. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with an aqueous bath consisting essentially of nickel ions and hypophosphite ions, said bath also containing sulfide ions and ion-s of a heavy metal that is non-catalytic for the oxidation of hypophosphite and that forms with said sulfide ions a thiocompound that is both stable and substantially insoluble in said bath, said thio-compo'und being present in solution in said bath only in a controlled trace amount not greater than about 200 parts per 1,000,000 parts of said bath by weight so as not substantially to reduce the plating rate of said bath and so as to maintain the dissociated sulfide ion concentration in said bath only in a controlled trace amount of the order of magnitude of 1 part per 100,000,000 parts of said bath by weight in order to inhibit random decomposition of said bath.

13. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with an aqueous bath consisting essentially of nickel ions and hypophosphite ions, said bath also containing a sulfide of a metal selected from the group consisting of lead, tellurium and tin, said metal sulfide being present in solution in said bath only in a controlled trace amount not greater than about 50 parts per 1,000,000 parts of said bath by weight so as not substantially to reduce the plating rate of said bath and so as to maintain the dissociated sulfide ion concentration in said bath only in a controlled trace amount of the order of magnitude of 1 part per 100,000,000 parts of said bath by weight in order to inhibit random decomposition of said bath.

14. The process of chemically plating With nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with an aqueous bath consisting essentially of nickel ions and hypophosphite ions, said bath also containing lead sulfide, said lead sulfide being present in solution in said bath only in a controlled trace amount not greater than about 5 parts per 1,000,000 parts of said bath by weight so as not substantially to reduce the plating rate of said bath and so as to maintain the dissociated sulfide ion concentration in said bath only in a controlled trace amount of the order of 1 part per 100,000,000 parts of said bath by weight in order to inhibit random decomposition of said bath.

15. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body With an aqueous bath consisting essentially of nickel ions and hypoyhosphite ions, said bath also containing sulfide ions and ions of lead, said sulfide ions and ions of lead being present in solution in said bath only in controlled trace amounts that together are not greater than about 5 parts per 1,000,000 parts of said bath by weight so as not substantially to reduce the plating rate of said bath and so as to maintain the dissociated sulfide ion concentration in said bath in a controlled trace amount of the order of magnitude of 1 part per 100,000,000 parts of said bath by weight in order to inhibit random decomposition of said bath.

16. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with an aqueous bath consisting essentially ofnickel ionsand hypophosphite ions, said bath also containing sulfide ions and ions of tellurium, said sulfide ions and ions of telluriurn being present in solution in said bath only in controlled trace amounts that together are not greater than about 200 parts per 1,000,000 parts of said bath by weight so as not substantially to reduce the plating rate of said bath and so as to maintain the dissociated sulfide ion concentration in said bath only in a controlled trace amount of the order of magnitude of 1 part per 100,000,000 parts of said bath by weight in order to inhibit random decom position of said bath.

17. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with an aqueous bath consisting essentially of nickel ions and hyp-ophosphite ions, said bath also containing sulfide ions and ions of tin, said sulfide ions and ions of tin being present in solution in said bath only in controlled trace amounts that together are not greater than about 125 parts per 1,000,000 parts of said bath by weight so as not substantially to reduce the plating rate of said bath and so as to maintain the dissociated sulfide ion concentration in said bath only in a controlled trace amount of the order of magnitude of 1 part per 100,000,000 parts of said bath by weight in order to inhibit random decomposition of said bath.

18. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body throughout a time interval with an aqueous bath consisting essentially of nickel ions and hypophosphite ions, said bath also containing lead sulfide, said lead sulfide being present in solution in said bath only in a controlled trace amount in the approximate range .5 to 5 parts per 1,000,000 parts of said bath by Weight so as not substantially to reduce the plating rate of said bath and so as to maintain the dissociated sulfide ion concentration in said bath only in a controlled trace amount of the order of 1 part per 100,000,000 parts of said bath by weight in order to inhibit random decomposition of said bath, and adding to said bath during said time interval trace quantities of both sulfide ions and lead ions so as to maintain said controlled trace amount of lead sulfide present in solution in said bath in said range set forth.

19. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with a hot aqueous bath consisting essentially of nickel ions and hypophosphi-te ions and also containing S" anions and Pbcations in controlled trace amounts that together are not greater than about parts per 1,000,000 parts of said bath by weight so as not substantially to reduce the plating rate of said bath, the temperature of said bath being above 90 C. and the pH of said bath being in the range 3.0 to 7.0, the P-b-- cation concentration in said bath being in the approximate range 0.5 to 5.0 parts per 1,000,000 parts of said bath by weight so as to maintain the dissociated S" anion concentration in said bath of the order of magnitude of 1 part per 100,000,000 parts of said bath by weight in order to inhibit random decomposition of said bath.

20. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with an aqueous bath comprising nickel ions and hypophosphite ions, said bath also containing some sulfur and a trace of lead in solution therein in order to inhibit random decomposition thereof without substantial reduction of the plating rate thereof,

said trace of lead in solution in said bath being in an amount by weight of at least /2 part but not in excess of 5 parts per 1,000,000 parts of said bath.

21. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with an aqueous bath comprising nickel ions and hypophosphite ions, said bath also containing some sulfur and a trace of lead in solution therein in order to inhibit random decomposition thereof without substantial reduction of the plating rate thereof, said trace of lead in solution in said bath being in an amount by weight of about 2 parts per 1,000,000 parts of said bath.

22. A bath for the chemical plating of a catalytic material with nickel consisting essentially of an aqueous solution of a nickel salt and a hypophosphite and an additive consisting of a thio-compound that forms an oriented hydrophobic film on said material, said additive being present in solution in said bath only in a controlled trace amount not greater than about 200 parts per 1,000,000 parts of said bath by weight so as not substantially to reduce the plating rate of said bath and so as to inhibit random decomposition of said bath.

23. The bath set forth in claim 22, wherein said additive consists essentially of a sulfhydric compound.

24. A bath for the chemical plating with nickel of a catalytic material consisting essentially of an aqueous solution of a nickel salt and a hypophosphite, said bath also containing a thio-cornpound that is both non-oatalytic for the oxidation of hypophosphite and stable in said bath, said thio-compound being present in solution in said bath only in a controlled trace amount in the approximate range 0.05 to 200 parts per 1,000,000 parts of said bath by weight so as not substantially to reduce the plating rate of said bath and so as to maintain the dissociated sulfide ion concentration in said bath only in a controlled trace amount of the order of magnitude of 1 part per 100,000,000 parts of said bath by weight in order to inhibit random decomposition of said bath.

25. A bath for the chemical plating with nickel of a catalytic material consisting essentially of an aqueous solution of a nickel salt and a hypophosphite, said bath also containing sulfide ions and ions of lead, said ions named being present in solution in said bath only in controlled trace amounts that together are not greater than about 5 parts per 1,000,000 parts of said bath by weight so as not substantially to reduce the plating rate of said bath and so as to maintain the dissociated sulfide ion concentration in said bath in a controlled trace amount of the order of magnitude of 1 part per 100,000,000 parts of said bath by weight in order to inhibit random decomposition of said bath.

26. A bath for the chemical plating with nickel of a catalytic material comprising an aqueous solution of a nickel salt and a hypophosph'ite, said bath also containing some sulfur and a trace of lead in solution therein in order to inhibit random decomposition thereof without substantial reduction of the plating rate thereof, said trace of lead in solution in said bath being in an amount by weight of at least /2 part but not in excess of 5 parts per 1,000,000 parts of said bath.

27. A bath for the chemical plating with nickel of a catalytic material comprising an aqueous solution of a nickel salt and a hypophosphite, said bath also containing some sulfur and a trace of lead in solution therein in order to inhibit random decomposition thereof without substantial. reduction of the plating rate thereof, said trace of lead in solution in said bath being in an amount by Weight of about 2 parts per 1,000,000 parts of said bath.

References Cited in the file of this patent UNITED STATES PATENTS Dec. 5, 1950 2,532,283 Brenner 

1. THE PROCESS OF CHEMICALLY PLATING, WITH NICKEL A BODY ESSENTIALLY COMPRISING AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF IRON, COBALT, NICKEL, ALUMINUM, COPPER, SILVER, GOLD, PALLADIUM AND PLATINUM, WHICH COMPRISES CONTACTING SAID BODY WITH AN AQUEOUS BATH CONSISTING ESSENTIALLY OF NICKEL IONS AND HYPOPHOSPHITE IONS AND ALSO CONTAINING SULFIDE IONS AND A SULFIDE ION CONTROLLER, BOTH SAID SULFIDE IONS AND SAID SULFIDE ION CONTROLLER BEING PRESENT IN SOLUTION IN SAID BATH ONLY IN CONTROLLED TRACE AMOUNTS THAT TOGETHER ARE NOT GREATER THAN ABOUT 200 PARTS PER 1,000,000 PARTS OF SAID BATH BY WEIGHT SO AS NOT SUBSTANTIALLY TO REDUCE THE PLATING RATE OF SAID BATH, SAID SULFIDE ION CONTROLLER FORMING WITH SAID SULFIDE IONS A THIO-COMPOUND THAT IS BOTH STABLE AND SUBSTANTIALLY INSOLUBLE IN SAID BATH SO AS TO MAINTAIN THE DISSOCIATED SULFIDE ION CONCENTRATION IN SAID BATH OF THE ORDER OF MAGNITUDE OF 1 PART PER 100,000,000 PARTS OF SAID BATH BY WEIGHT IN ORDER TO INHIBIT RANDOM DECOMPOSITION OF SAID BATH. 